Looking to improve your preparation with TNPSC Physics Energy questions? You’re in the right place! This TNPSC Physics Energy Test 4 is designed to help you strengthen important Energy concepts through carefully selected physics questions that match the TNPSC exam pattern. Whether you’re revising or taking a TNPSC free online test to check your knowledge, these multiple-choice questions with answers and explanations will help you build confidence and score better in the General Science section.
TNPSC Physics Energy Test 4 – All Questions Explanations
This TNPSC Physics Energy quiz covers important General Science topics such as the commercial unit of electrical energy, electrical energy, heat energy, mechanical energy, the law of conservation of energy, energy conversions, work–energy relationships, and their real-life applications. These physics questions are prepared in the TNPSC exam pattern to strengthen conceptual understanding, analytical thinking, and problem-solving skills. Use this TNPSC free online test to improve your preparation for TNPSC Group 2, Group 2A, Group 4, and other competitive examinations.
1. Which unit is commonly used to measure electrical energy consumed in houses?
Answer: C. Kilowatt-hour
Explanation:
Electrical energy consumed in homes is measured in kilowatt-hour (kWh), which is the commercial unit of electrical energy. One kilowatt-hour is the energy used by a 1000 W appliance operating for one hour. Electricity bills are calculated based on the total number of kilowatt-hours consumed.
Quick Revision
- Commercial unit of electrical energy = kilowatt-hour (kWh).
- SI unit of energy = Joule.
- 1 kWh = Energy used by a 1000 W appliance in one hour.
- Electricity bills are calculated in kWh.
Real-Life Example
A 1000 W electric heater running for one hour consumes 1 kWh of electrical energy.
2. Which device converts electrical energy directly into heat energy?
Answer: A. Electric iron
Explanation:
An electric iron converts electrical energy directly into heat energy using a high-resistance heating element. When electric current passes through the element, heat is produced due to the heating effect of electric current. This heat is then transferred to the metal soleplate, which is used for ironing clothes.
Quick Revision
- Electric iron converts electrical energy into heat energy.
- It works on the heating effect of electric current.
- Heating elements are made of high-resistance materials like nichrome.
- Heat produced is used to press clothes.
Real-Life Example
When you switch on an electric iron, its soleplate becomes hot within a few minutes, making it easy to remove wrinkles from clothes.
3. A stretched bow possesses mainly:
Answer: C. Elastic potential energy
Explanation:
When a bow is stretched, work is done against its elasticity, storing energy in the bow. This stored energy is called elastic potential energy. When the string is released, the stored energy is converted into the kinetic energy of the arrow.
Quick Revision
- Elastic potential energy is stored in stretched or compressed objects.
- A stretched bow stores elastic potential energy.
- Stored energy is converted into kinetic energy when released.
- Elastic materials regain their original shape after the force is removed.
Real-Life Example
A stretched rubber band also stores elastic potential energy, which is released when the band is let go.
4. During braking, the kinetic energy of a moving vehicle is mainly converted into:
Answer: B. Heat energy
Explanation:
When brakes are applied, friction is produced between the brake pads and the wheels. This friction converts the vehicle’s kinetic energy into heat energy, slowing down and eventually stopping the vehicle. A small amount of energy is also produced as sound.
Quick Revision
- Braking involves friction.
- Kinetic energy is mainly converted into heat energy.
- Friction slows down moving objects.
- Heat is generated in the brake system during braking.
Real-Life Example
After driving for a long distance, the brake discs of a car become hot because of the heat produced by friction.
5. Which of the following best illustrates the law of conservation of energy?
Answer: B. A swinging pendulum
Explanation:
A swinging pendulum continuously converts potential energy into kinetic energy and back again. At the highest point, potential energy is maximum, while at the lowest point, kinetic energy is maximum. Although the forms of energy change, the total mechanical energy remains nearly constant, demonstrating the law of conservation of energy.
Quick Revision
- Energy cannot be created or destroyed.
- A pendulum continuously converts potential energy into kinetic energy.
- Total mechanical energy remains constant in the absence of friction.
- This demonstrates the law of conservation of energy.
Real-Life Example
A child on a playground swing experiences the same energy conversion between potential and kinetic energy during each swing.
6. Which appliance consumes the highest electrical energy if used for one hour?
Answer: C. 1000 W heater
Explanation:
The electrical energy consumed by an appliance depends on its power rating and the duration of use. If all the given appliances are operated for one hour, the 1000 W heater consumes the highest amount of electrical energy because it has the highest power rating. Higher power appliances use more electricity in the same period.
Quick Revision
- Electrical Energy = Power × Time.
- Higher power rating means higher energy consumption.
- Power is measured in watts (W).
- Electrical energy is billed in kilowatt-hours (kWh).
Real-Life Example
Running a 1000 W heater for one hour consumes much more electricity than using a 40 W LED bulb for the same duration.
7. Which energy conversion occurs in an electric motor?
Answer: B. Electrical → Mechanical
Explanation:
An electric motor converts electrical energy into mechanical energy. It works on the principle that a current-carrying conductor placed in a magnetic field experiences a force, causing the motor to rotate. This mechanical motion is used to operate many electrical appliances.
Quick Revision
- Electric motor converts electrical energy into mechanical energy.
- Works using the magnetic effect of electric current.
- Produces rotational motion.
- Used in household and industrial appliances.
Real-Life Example
The motor inside an electric fan converts electrical energy into the mechanical energy needed to rotate the blades.
8. Which of the following is an example of mechanical energy?
Answer: A. Water flowing in a river
Explanation:
Mechanical energy is the sum of kinetic energy and potential energy. Flowing river water possesses kinetic energy because it is in motion. This moving water can perform work, such as rotating turbines in hydroelectric power plants, making it an example of mechanical energy.
Quick Revision
- Mechanical energy = Kinetic energy + Potential energy.
- Flowing water has kinetic energy.
- Mechanical energy enables objects to do work.
- Hydroelectric power uses the mechanical energy of water.
Real-Life Example
Water released from a dam spins turbines to generate electricity in a hydroelectric power station.
9. Which statement is correct?
Answer: C. Energy changes from one form to another.
Explanation:
According to the law of conservation of energy, energy cannot be created or destroyed. It can only be transformed from one form into another. Every machine and natural process involves the conversion of energy while the total amount of energy remains constant.
Quick Revision
- Energy cannot be created or destroyed.
- Energy only changes from one form to another.
- Total energy remains constant.
- This principle is called the law of conservation of energy.
Real-Life Example
An electric bulb converts electrical energy into light energy and heat energy without creating new energy.
10. In an electric heater, the heating element is chosen because it has:
Answer: B. High resistance
Explanation:
The heating element in an electric heater is made of a material such as nichrome, which has high electrical resistance. When electric current flows through it, more electrical energy is converted into heat due to the heating effect of electric current. This makes the heater efficient in producing heat.
Quick Revision
- Heating elements have high electrical resistance.
- Nichrome is commonly used in electric heaters.
- High resistance produces more heat.
- Electric heaters work on the heating effect of electric current.
Real-Life Example
The nichrome coil inside an electric room heater becomes red hot after switching it on, providing warmth during cold weather.
11. Which of the following energy conversions takes place in an electric bulb?
Answer: A. Electrical → Light & Heat
Explanation:
An electric bulb converts electrical energy mainly into light energy and also produces heat energy. In an incandescent bulb, the filament becomes white hot when electric current passes through it, emitting light. However, a significant amount of electrical energy is also released as heat.
Quick Revision
- Electric bulb converts electrical energy into light and heat.
- Incandescent bulbs produce more heat than LED bulbs.
- Light is the useful output energy.
- Heat is a by-product of energy conversion.
Real-Life Example
A glowing incandescent bulb becomes hot after being switched on for a few minutes because part of the electrical energy is converted into heat.
12. Which quantity is measured in kilowatt-hour (kWh)?
Answer: C. Electrical energy
Explanation:
The kilowatt-hour (kWh) is the commercial unit used to measure electrical energy consumed by homes, industries, and commercial buildings. It represents the energy consumed when a 1000 W appliance operates continuously for one hour and is the unit used for electricity billing.
Quick Revision
- kWh is the commercial unit of electrical energy.
- 1 kWh = 1000 watt-hours.
- Electricity consumption is measured in kWh.
- SI unit of energy is Joule.
Real-Life Example
If a 1000 W electric geyser runs for one hour, it consumes 1 kWh of electrical energy.
13. Which one of the following devices converts mechanical energy into electrical energy?
Answer: B. Generator
Explanation:
A generator converts mechanical energy into electrical energy through electromagnetic induction. When a turbine or engine rotates the generator shaft, electrical energy is produced. Generators are widely used in hydroelectric, thermal, and wind power stations.
Quick Revision
- Generator converts mechanical energy into electrical energy.
- Works on the principle of electromagnetic induction.
- Used in power generation.
- Turbines drive generators.
Real-Life Example
In a hydroelectric power plant, flowing water rotates turbines that drive generators to produce electricity.
14. Which statement about mechanical energy is correct?
Answer: C. It is the sum of kinetic and potential energy.
Explanation:
Mechanical energy is the total energy possessed by an object due to its motion (kinetic energy) and position (potential energy). Both forms of energy together determine the object’s ability to perform work. In many systems, the total mechanical energy remains constant if friction is absent.
Quick Revision
- Mechanical energy = Kinetic energy + Potential energy.
- Kinetic energy depends on motion.
- Potential energy depends on position or height.
- Total mechanical energy is conserved in ideal conditions.
Real-Life Example
A roller coaster has maximum potential energy at the top of a hill and maximum kinetic energy at the bottom, while its total mechanical energy remains nearly constant.
15. A battery-operated torch mainly converts:
Answer: A. Chemical → Light
Explanation:
A battery stores chemical energy, which is first converted into electrical energy when the circuit is completed. The bulb or LED in the torch then converts the electrical energy into light energy. Overall, the main energy conversion is from chemical energy to light energy.
Quick Revision
- Batteries store chemical energy.
- Chemical energy is converted into electrical energy.
- Electrical energy produces light.
- Torch is a common example of energy conversion.
Real-Life Example
When you switch on a flashlight during a power cut, the battery’s stored chemical energy is converted into light, allowing you to see in the dark.
16. Which of the following appliances mainly converts electrical energy into mechanical energy?
Answer: A. Electric fan
Explanation:
An electric fan converts electrical energy into mechanical energy using an electric motor. When electric current flows through the motor, it rotates the fan blades, producing airflow. This is a common example of electrical energy being converted into mechanical motion.
Quick Revision
- Electric fan converts electrical energy into mechanical energy.
- It works with the help of an electric motor.
- Mechanical energy is produced as rotational motion.
- Fans, mixers, and pumps use electric motors.
Real-Life Example
When you switch on a ceiling fan, its motor rotates the blades to circulate air throughout the room.
17. Which of the following consumes the least electrical energy in one hour?
Answer: A. 40 W lamp
Explanation:
Electrical energy consumption depends on the power rating of the appliance and the time it is used. Since all the given appliances operate for one hour, the 40 W lamp consumes the least electrical energy because it has the lowest power rating.
Quick Revision
- Lower power rating means lower energy consumption.
- Electrical Energy = Power × Time.
- Power is measured in watts (W).
- Energy consumption is measured in kilowatt-hours (kWh).
Real-Life Example
An LED lamp with a low power rating uses much less electricity than an electric heater when both are operated for the same duration.
18. Which statement is correct regarding electrical energy consumption?
Answer: A. Higher power appliances consume more energy in the same time.
Explanation:
The amount of electrical energy consumed depends on both the power rating of the appliance and the duration of use. If two appliances are used for the same amount of time, the appliance with the higher power rating consumes more electrical energy.
Quick Revision
- Electrical Energy = Power × Time.
- Higher power means higher energy consumption.
- Longer usage increases electricity consumption.
- Electricity bills depend on total energy used.
Real-Life Example
Using a 2000 W electric heater for one hour consumes much more electricity than using a 100 W television for the same period.
19. In a hydroelectric power station, the generator converts:
Answer: A. Mechanical → Electrical
Explanation:
In a hydroelectric power station, flowing water rotates a turbine, producing mechanical energy. The generator then converts this mechanical energy into electrical energy through the principle of electromagnetic induction. The electricity generated is supplied to homes and industries.
Quick Revision
- Generator converts mechanical energy into electrical energy.
- Hydroelectric plants use the energy of flowing water.
- Turbines rotate the generator shaft.
- Electromagnetic induction is the working principle of generators.
Real-Life Example
Water released from a dam spins large turbines, enabling generators to produce electricity for nearby cities and villages.
20. Which of the following best demonstrates the law of conservation of energy?
Answer: B. Energy changes from one form to another.
Explanation:
The law of conservation of energy states that energy can neither be created nor destroyed. It can only be transformed from one form into another while the total amount of energy remains constant. This principle applies to all physical, chemical, and biological processes.
Quick Revision
- Energy cannot be created or destroyed.
- Energy only changes from one form to another.
- Total energy remains constant.
- The law of conservation of energy is a fundamental law of physics.
Real-Life Example
A hydroelectric power plant converts the potential energy of stored water into kinetic energy, then mechanical energy, and finally electrical energy without creating or destroying energy.
Further Reading
To strengthen your understanding of TNPSC Physics Energy, refer to the official NCERT Class 9 Science – Work and Energy chapter. It explains key concepts such as work, power, kinetic energy, potential energy, the law of conservation of energy, and the commercial unit of electrical energy, which form the foundation for many TNPSC General Science questions.
